1. Field of the Invention
This invention relates to electromagnetic detectors. More specifically, it relates to an improved detector that provides an indication of the angle of incidence of electromagnetic energy.
While the present invention is described herein with reference to particular optical embodiments, it should be understood that the invention is not limited thereto. The optic receiver of the present invention may be adapted and employed for a variety of electromagnetic requirements as those skilled in the art will recognize in light of the present disclosure.
2. Description of the Prior Art
Conventional techniques for obtaining the azimuth or angle of incidence of optical or other electromagnetic energy typically utilize either an array of directional detectors or a single directional detector adapted to rotate through the target plane.
The array approach requires the use of a plurality of highly directional receivers. Each receiver is assigned a section of the area to be scanned. In an optical system, each receiver would include a photodetector and associated electronic circuit so that any optical energy detected made by the receiver would be electrically interpreted as coming from a predetermined direction.
Obviously, this approach can be costly where accurate angle determinations must be made. That is, the cost/performance of such a system would depend on the number of detectors or receivers required. Moreover, no matter how many receiver elements are utilized, accuracy would be limited by the inherent shortcomings of a discrete system. That is, it is impossible to determine exactly where the image is within the assigned sector.
These shortcomings can be avoided somewhat by utilizing the rotating receiver approach of the alternative technique. Here a highly directional receiver element is mounted for rotation so that a single receiver element can scan the desired area. This technique can be somewhat more accurate than that of the dedicated array insofar as the exact angle at which the element is pointing is known. However, the rotating element approach suffers from limitations common to mechanical systems, i.e., speed and durability.
The response time of a system utilizing this technique would be much longer than that of the dedicated array. Actual response could be improved somewhat by using several receiver elements, however, where ultra fast response is required this solution probably would not justify the additional cost.
In addition, the mechanical nature of a rotating element system would limit its reliability over a long period of use.
A third approach calls for the utilization of linear detector arrays with complicated lenses having a fairly high resolution over large fields of view. Such lenses are currently so expensive as to minimize their cost effectiveness for most conventional applications.